1. Field of the Invention
The present invention relates to a wafer polishing apparatus for chemical mechanical polishing, and a wafer polishing method.
2. Description of the Related Art
Wafers for semiconductor equipments and electronic components are manufactured through processings including cutting, polishing, and the like. Recently, development of semiconductor technology has promoted miniaturization and multi-layer wiring in a design rule for semiconductor integrated circuit, and larger diameter wafers have been used from the view of reducing costs. In such a context, when a pattern layer is formed on a previous pattern layer in a conventional way, due to the concavo-convex profile of the previous pattern layer, it is difficult to form an accurate pattern thereon, which often leads to defects.
So, a planarization process has been used to planarize a surface of a pattern formed layer before another pattern layer is formed thereon. In the planarization process, frequently chemical mechanical polishing (CMP) is used. When a wafer is polished in chemical mechanical polishing, a wafer carrier head carries the wafer and holds the wafer against a rotating polishing pad at a predetermined pressure, and then a polishing liquid such as slurry or chemical is supplied between the polishing pad and the wafer.
In the polishing by chemical mechanical polishing, a polishing liquid supplied onto the polishing pad is a significant factor which influences the result of polishing, and a consistent supply of a polishing liquid to a polishing pad is required to uniformly polish wafers.
Because an oversupply of a polishing liquid increases the cost for polishing, a consistent supply of a polishing liquid needs to be effectively performed by a small amount of a polishing liquid to a polishing pad.
Conventionally, to address the above problem, grooves are formed in a polishing pad to effectively distribute a polishing liquid over an entire surface of the polishing pad, and the grooves are in shapes having various designs (see a document: G. P. Muldowney, Optimization of CMP Pad Groove Arrays for Improved Slurry Transport, Wafer Profile Correction, and Defectivity Reduction, Proceeding of CMP-MIC (2005). pp 156-167).
However, a polishing liquid needs to be transported to a surface of a polishing pad, not into the grooves, for polishing. Therefore, there has been a need for a method to effectively supply a polishing liquid to a surface of a polishing pad, not into grooves formed in the polishing pad.
In order to address the problem, apparatuses such as a wafer polishing apparatus in which a position to supply a polishing liquid can be changed by using a movable arm, and a polishing apparatus in which a polishing liquid is sprayed in a form of mist and a squeegee is provided to spread the polishing liquid on a surface to be polished have been suggested (for example, see Japanese Patent Application Laid-Open No. 2004-63888, Japanese Patent Application Laid-Open No. 11-70464, and Japanese Patent Application Laid-Open No. 10-296618).